Apoptosis is a mechanism for programmed cell death that typically occurs during embryogenesis, development and during the normal physiological response to aging. Apoptosis can also be triggered in response to a cell stressor, such as heat, radiation, nutrient deprivation, viral infection, hypoxia, increased intracellular calcium concentration and in response to certain glucocorticoid receptor activation.
Apoptosis, in part, initiates activation of one or more caspase signaling pathways. Caspases are strong proteases that cleave after aspartic acid residues and once activated, are responsible for proteolytic cleavage of a broad spectrum of cellular targets that ultimately lead to cell death.
Defective apoptosis regulation can lead to a variety of disorders. For example, impaired apoptotic activity can lead to inappropriate cell survival, and is associated with tumor growth, cancer, autoimmune disease, and inflammatory disease. Conversely, pathologically high levels of apoptosis can result in abnormal initiation of cell death pathways, as observed in e.g., neurodegenerative diseases (e.g., Parkinson's disease, Alzheimer's disease, dementia, and cerebral ischemia, among others) and infection (e.g., AIDS).